The present invention relates to discharge or barrier valves in the delivery chute of a coal-fired power facility between the exhauster fan and riffle box.
Coal-fired power generating facilities commonly use a combustion chamber fed with dustlike coal fines by multiple burner nozzles spaced uniformly around the chamber. It is critical to balance the flow from the burner nozzles to the fireball in the combustion chamber. Imbalances in this flow can result in NOX formation, erosion of boiler tubes in the combustion chamber, and LOI (loss on ignition) contamination of the saleable ash by-product.
The burner nozzles are fed with coal fines by a series of branched delivery chutes which typically emanate from a single source such as an exhauster fan. The exhauster fan provides suction and air flow necessary to pull coal fines from a mill or pulverizer and send them through the branched delivery pipes to the burner nozzles in the combustion chamber.
The centrifugal nature of the exhauster fan typically results in a separation of the coal fines into light and heavy flow distributions as they leave the fan. Each branching of the delivery pipe typically includes a xe2x80x9criffle boxxe2x80x9d of alternately angled diverters or plates whose function is to evenly redirect the flow of coal fines into the two branches. The uneven heavy/light distribution of fines leaving the exhauster fan, however, defeats the purpose of the riffle boxes.
The problem of heavy/light flow distributions of coal fines between the exhauster fan and the first riffle box is further exacerbated by the typical barrier valve plate in the delivery pipe between the exhauster fan and riffle box. The plane of the valve plate bisects the chute in a manner physically dividing the heavy and light distributions.
The present invention solves the problem of heavy/light distributions of coal fines between the exhauster fan outlet and the first riffle box in the delivery chute by (1) reorienting the valve plate axis at right angles to the axis of the exhauster fan, thereby splitting the coal flow in the pipe into identical xe2x80x9cupperxe2x80x9d and xe2x80x9clowerxe2x80x9d halves, each of which has a heavy/light distribution across the diameter of the pipe; and (2) providing the reoriented valve plate with diffuser elements on top and bottom surfaces thereof to radially redirect the heavy and light distributions in the top and bottom flows to merge and mix into a uniformly distributed flow upon reaching the riffle box.
In a preferred form the diffuser elements comprise an array of differently-sized semicircular diffuser elements on top and bottom surfaces of the valve plate.
In another aspect of the invention, an initial xe2x80x9ckickerxe2x80x9d diffuser element is located on the heavy distribution side of the entrance to the valve, preferably forming a peripheral semicircle on the heavy distribution side.
In yet a further aspect of the invention, peripheral diffuser elements are secured directly to the inside circumference of the portion of the chute which defines the valve plate housing, located to engage the edge circumference of the valve plate in the valve closed position to define one or more mechanical stops around the edge of the valve plate and further giving a sealing effect around the edge of the valve plate in the closed position.
These and other features and advantages of the invention will become apparent upon further reading of the specification, in light of the accompanying drawings.